1. Field of the Invention
The present invention relates to an optical disc player, such as an optomagnetic disc unit and compact disc unit, and particularly to a vibration preventive device which is designed to retard the vibration created in the source of drive force, which is made up of coils and magnets, from being transmitted to the stationary part.
2. Description of Related Art
FIG. 8 shows the focus correction device of the optical disc player.
In the figure, symbol 1 denotes a lens holder, by which an objective lens 2 is held. The objective lens 2 confronts the recording surface of the optical disc, and a laser beam from the objective lens 2 is projected on to the recording surface of the optical disc, resulting in the formation of a small light spot on the recording surface. The focus correction device shown in FIG. 8 is a servo system to make the laser beam spot projected by the objective lens 2 in-focus on the recording surface. The lens holder 1 is supported by a support member 3 such as a flat spring, and is movable finely in the direction of the optical axis (Y direction) of the objective lens 2. Focus coils 4 are provided on both sides of the lens holder 1. The support member 3 has its base supported by a pickup chassis 5 which is the stationary part of the device. Fixed on the pickup chassis 5 are U-shaped yokes 6, with a magnet 7 being fixed on the interior surface of the outer section of the yoke 6. By controlling the current flowing in the horizontal direction (orthogonal to the Y direction) in the focus coil 4, the lens holder 1 is driven for focus correction in the Y direction.
FIG. 7 shows in a sense of model the above-mentioned conventional focus correction device. This device operates to apply a drive force F.sub.1 to the focus coil 4 provided on the lens holder 1 by means of the magnet 7 provided on the pickup chassis 5. The drive force F.sub.1 has a counter force F.sub.2, which is transmitted directly to the pickup chassis 5. In the focus correcting drive operation, the lens holder 1 is driven at current frequencies ranging from d.c. to several thousand Hz, and therefore the counter force F.sub.2 is transmitted to the pickup chassis 5 as vibrations having frequencies related to the above-mentioned driving frequencies.
Transmission of such vibration to the pickup chassis 5 creates various problems.
For example, the vibration is propagated from the stationary pickup chassis 5 to the guide rail which supports the pickup chassis 5 movably, to the main chassis of the disc apparatus, and finally to the optical disc. Since the optomagnetic disc has a natural frequency of about 1.4 kHz, the above mentioned vibration will develop a problem of resonation of the disc, and the disc resonation will adversely affect the focus correcting operation of the lens holder 1.